1. Field of the Invention
The present invention relates to a hinge and, especially, to a hinge mounted between a cover and a body of an electronic device to allow the cover to pivot relative to the body.
2. Description of the Prior Arts
The conventional hinge is mounted between a cover and a body of an electronic device. Conventional hinges have disclosed various structures to provide torque variation so that the force exerted by users to open the cover varies accordingly, and that does help users to easily open/close the cover. Also, said conventional structure has to provide a positioning function in a manner such that the cover of the electronic device can be kept at certain visual angle. In general, in order to achieve the above function, there are two kinds of the hinge structures: (1) a structure with a resilient sleeve embracing a pintle, both having corresponding flat surfaces to be selectively engaged with each other, during the rotation of the pintle, as the positioning function, and (2) a structure with a stationary positioning washer (called a cam) non-rotatably mounted on a pintle and a rotating positioning washer rotatably mounted on the pintle, each having corresponding protrusions and detents to be engaged to generate the torque variation and positioning function.
With reference to FIG. 11, the torque provided by the conventional hinge with the resilient sleeve and the pintle both having corresponding flat surfaces changes with the rotating angle of the cover relative to the body. Suppose that the torque is positive when the cover is opening and that the torque is negative when the cover is closing. At the very beginning, the cover is closed relative the body, and the flat surface of the resilient sleeve faces and engages with flat surface of the pintle so that the conventional hinge provides a largest torque when the cover starts to be pivoted to open. Once the cover is pivoted over 12 degrees, the flat surfaces of the resilient sleeve and the pintle are separated. Then, the torque is decreased until the cover is pivoted at about 35 degrees. When the cover is pivoted over 35 degrees, the conventional hinge provides a constant torque. When the cover is being closed and the included angle between the cover and the body is less than 10 degrees, the corresponding flat surfaces engage with each other so that the torque decreases rapidly to urge the cover closing quickly. Therefore, the user needs to provide a certain force to open the cover. Further, the cover quickly closing causes the latching between the cover and the body to be firm. Another conventional hinge with positioning washers having corresponding protrusions and detents also has a similar torque variation as shown in FIG. 11.
Generally, when the cover is pivoted over 35 degrees, both conventional hinges are capable of holding the cover with its weight at a certain visual angle even though the torque is less than the largest torque. However, with the popularity of the electronic device and the development of the touch panel, the touch panel is widely mounted in the cover to replace the traditional display panel. When the user acts on the touch panel, the cover bears extra force besides its own weight. The conventional hinges do not provide enough torque to hold the cover with extra force. Thus, the conventional hinge is not suitable for the cover with a touch panel.